UsePD Meter is a digital precision optical instrument used to measure distance between human pupils in the process of optometry.CharacteristicsThis device is designed in a scientific and reasonable way, integrating technologies on optics, microelectronics.Technical Parameters :Range of data display: Binocular pupillary distance4483mm , Left or right pupillary distance2241.5mmEffective range of measurementBinocular pupillary distance4582mm, Left or right pupillary distance22.541mmIndication error0.5mmRounding error0.5mmDistance of target30cmPower source:Voltage DC 6V, 4 AA batteryTime for automatic shut-off1 and a half minutes after stopping operationOverall dimensions: 219mm(L)169mm(W)86mm(H)Weight: 0.7kg